The proposed research is designed to investigate the ability of the primate corpus luteum to produce prostaglandins, and the role of these substances in the regulation of luteal function during early pregnancy. The specific aims are: 1) to identify and characterize the prostaglandins produced by the corpus luteum of the rhesus monkey, and possible stimulators/inhibitors of prostaglandin production, 2) to assess luteal prostaglandin production throughout simulated early pregnancy, and to correlate such production with basal and gonadotropin stimulated luteal steroid and relaxin secretion, and 3) to block luteal prostaglandin synthesis during simulated early pregnancy, and monitor the effects of this blockade on the decline in progesterone and the increase in relaxin secretion by the corpus luteum. To induce simulated early pregnancy, non-pregnant monkeys will be injected intramuscularly with increasing doses of human chorionic gonadotropin for 10 days in a regimen that has invoked patterns and concentrations of chorionic gonadotropin resembling those of early pregnancy. Treatment will begin during the expected time of implantation (8-10 days after the midcycle luteinizing hormone surge). Initially, prostaglandins produced by dispersed luteal cells during short term incubations will be identified using gas chromatography with electron-capture detection. Subsequent studies will employ radioimmunoassays (RIA) of the potentially important luteal prostaglandins. RIAs will also be used to measure progesterone, estradiol-17Beta, and relaxin concentrations in cells, media, and serum. The proposed research will provide the first detailed information on the prostaglandin synthetic capacity of primate luteal cells and the role of luteal prostaglandins in the regulation of the primate corpus luteum of early pregnancy. Such knowledge has the potential to provide the basis for improved control of fertility regulation at the level of the corpus luteum of early pregnancy.